Lung cancer is the leading cause of cancer mortality worldwide. Abnormal oncogenic activation of EGFR signaling is one of major driver molecules for triggering lung cancer, small molecule tyrosine kinase inhibitors (TKI) have provided benefit for lung cancer patients, and radiation treatments are commonly used to improve the patient outcome. Recent studies from our laboratories show that oxidative stress and altered miRNA expression are important in therapeutic responses to radiation and chemotherapy. Our preliminary results demonstrate that persistent p70S6K1 activation and oxidative stress play an important role in resistant lung cancer cells upon TKI and radiation treatments, but not in sensitive cells. We also showed higher expression levels of NOX4 and EZH2 in the resistant cells that are resistant to TKI and radiation treatments. We hypothesize that p70S6K1 is induced by NOX4 and EZH2 overexpression, and miR-152 suppression and MDM2 are key downstream effectors for regulating lung cancer development and therapeutic resistance to targeted therapy and radiation treatment. We plan to test this hypothesis through three aims. Aim 1 is to determine role and mechanism of p70S6K1 in therapeutic resistance to TKI-targeted therapy and radiation treatment, and to identify p70S6K1 upstream regulators and downstream effectors for transmitting signal(s) for the treatment resistance. Aim 2 is to determine whether p70S6K1 induces lung tumor growth and TKI-targeted therapeutic resistance through MDM2 and miR-152 suppression using a lung orthotopic tumor model; and to determine whether p70S6K1 and NOX4 are required for tumor development using human lung cancer Patient-Derived Tumor (PDX) model. Aim 3 is to investigate whether levels of p70S6K1, NOX4, MDM2, and/or miR-152 are correlated with TKI-targeted therapy responses in lung cancer cohort; and are correlated with human lung cancer stages and survival; and to determine whether p70S6K1 regulates tumor angiogenesis through VEGF using a humanized chimeric tumor model. This R01 proposal will help to understand divergent resistant mechanisms in response to EGFR-TKI and radiation therapy. The successful completion of proposal will provide better understanding of lung cancer resistant mechanism and potential novel therapeutic option for lung cancer treatment in the future.